chemistry : class11 Solubility of Sparingly Soluble Salts : Common ion effect : Equilibrium MCQ Questions and Answers
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Solubility of Sparingly Soluble Salts
MCQ questions and answers.
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MCQ Questions
1. What happens to the solubility of a sparingly soluble salt when a soluble salt containing a common ion is added?
A.
It increases
B.
It decreases
C.
It remains unchanged
D.
It becomes infinite
Correct Answer:
It decreases
Explanation:
The addition of a common ion shifts the dissolution equilibrium of the sparingly soluble salt toward the solid, decreasing its solubility.
2. For the dissolution equilibrium AgCl(s) ⇌ Ag⁺(aq) + Cl⁻(aq), which ion acts as a common ion when NaCl is added?
A.
Na⁺
B.
Ag⁺
C.
Cl⁻
D.
NaCl
Correct Answer:
Cl⁻
Explanation:
Chloride ions are already present in the dissolution equilibrium of AgCl, so Cl⁻ from NaCl is the common ion.
3. The solubility product expression for the sparingly soluble salt BaSO₄ is:
A.
Ksp = [Ba²⁺][SO₄²⁻]
B.
Ksp = [BaSO₄]
C.
Ksp = [Ba²⁺] + [SO₄²⁻]
D.
Ksp = [BaSO₄][Ba²⁺][SO₄²⁻]
Correct Answer:
Ksp = [Ba²⁺][SO₄²⁻]
Explanation:
For BaSO₄(s) ⇌ Ba²⁺(aq) + SO₄²⁻(aq), the solid is omitted from the equilibrium expression, giving Ksp = [Ba²⁺][SO₄²⁻].
4. If the solubility of AgCl in pure water is s mol L⁻¹, what is the concentration of Ag⁺ at equilibrium?
A.
0 mol L⁻¹
B.
s mol L⁻¹
C.
2s mol L⁻¹
D.
s² mol L⁻¹
Correct Answer:
s mol L⁻¹
Explanation:
AgCl dissolves in a 1:1 ratio to form Ag⁺ and Cl⁻, so the concentration of Ag⁺ is equal to its molar solubility, s.
5. For the salt AgCl, Ksp is 1.0 × 10⁻¹⁰. Its molar solubility in pure water is:
A.
1.0 × 10⁻¹⁰ mol L⁻¹
B.
1.0 × 10⁻⁵ mol L⁻¹
C.
1.0 × 10⁻² mol L⁻¹
D.
1.0 × 10⁻¹⁵ mol L⁻¹
Correct Answer:
1.0 × 10⁻⁵ mol L⁻¹
Explanation:
For AgCl, Ksp = s². Therefore, s = √(1.0 × 10⁻¹⁰) = 1.0 × 10⁻⁵ mol L⁻¹.
6. Which solution will generally contain the least dissolved AgCl?
A.
Pure water
B.
A solution containing AgNO₃
C.
A solution containing KNO₃
D.
A solution containing glucose
Correct Answer:
A solution containing AgNO₃
Explanation:
AgNO₃ provides Ag⁺, a common ion of AgCl. The common ion effect decreases the solubility of AgCl.
7. For the equilibrium CaF₂(s) ⇌ Ca²⁺(aq) + 2F⁻(aq), which substance decreases the solubility of CaF₂ by providing a common ion?
A.
NaCl
B.
KNO₃
C.
NaF
D.
NH₄NO₃
Correct Answer:
NaF
Explanation:
NaF dissociates to produce F⁻, which is a common ion in the dissolution equilibrium of CaF₂. This decreases the solubility of CaF₂.
8. When a sparingly soluble salt is added to water, it dissolves until:
A.
All the solid disappears
B.
The ionic product equals its Ksp
C.
The solution becomes neutral
D.
The temperature becomes zero
Correct Answer:
The ionic product equals its Ksp
Explanation:
At equilibrium with undissolved solid, the ionic product of the dissolved ions becomes equal to the solubility product, Ksp.
9. The solubility of BaSO₄ is lower in a solution containing Na₂SO₄ than in pure water because:
A.
Na₂SO₄ removes Ba²⁺ ions
B.
SO₄²⁻ is a common ion
C.
Na⁺ reacts with BaSO₄
D.
Water becomes a stronger solvent
Correct Answer:
SO₄²⁻ is a common ion
Explanation:
Na₂SO₄ increases the concentration of SO₄²⁻, a common ion in the dissolution equilibrium of BaSO₄, thereby decreasing its solubility.
10. If the solubility product of a salt is exceeded in a solution, what is expected to happen?
A.
The salt completely dissolves
B.
The solution becomes unsaturated
C.
The salt precipitates
D.
The salt changes into a gas
Correct Answer:
The salt precipitates
Explanation:
When the ionic product is greater than Ksp, the solution is supersaturated and excess ions combine to form a precipitate of the sparingly soluble salt.
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